public class MySingleLinkedList {
    class ListNode{
        public int val;
        public ListNode next;

        public ListNode(int val) {
            this.val = val;

        }
    }
    public ListNode head;//代表链表头节点


    public void display() {
        ListNode cur = head;
        while (cur != null) {
            System.out.print(cur.val+" ");
            cur = cur.next;
        }
        System.out.println();
    }


    public int size(){
        int count = 0;
        ListNode cur = head;
        while (cur != null) {
            count++;
            cur = cur.next;
        }
        return count;
    }
    public void addFirst(int val){
        ListNode node = new ListNode(val);
        node.next = head;
        head = node;
    }
    public void addLast(int val) {
        ListNode node = new ListNode(val);
        if(head==null){
            head=node;
            return;

        }
        ListNode cur =head;
        while (cur.next !=null){
            cur = cur.next;
        }
        cur.next=node;

    }
    public void addIndex(int index,int val) {
        //1.判断index的合法性
        try {
            checkIndex(index);
        }catch (IndexNotLegalException e) {
            e.printStackTrace();
        }
        //2.index == 0  || index == size()
        if(index == 0) {
            addFirst(val);
            return;
        }
        if(index == size()) {
            addLast(val);
            return;
        }
        //3. 找到index的前一个位置
        ListNode cur = findIndexSubOne(index);
        //4. 进行连接
        ListNode node = new ListNode(val);
        node.next = cur.next;
        cur.next = node;
    }
    private ListNode findIndexSubOne(int index) {
        int count = 0;
        ListNode cur = head;
        while (count != index-1) {
            cur = cur.next;
            count++;
        }
        return cur;
    }

    private void checkIndex(int index) throws IndexNotLegalException{
        if(index < 0 || index > size()) {
            throw new IndexNotLegalException("index不合法");
        }
    }
    public boolean contains(int val) {
        ListNode cur = head;
        while (cur != null) {
            if(cur.val == val) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }
    public void remove(int val){
        if(head == null){
            return;
        }
        if (head.val==val){
            head = head.next;
            return;
        }
        ListNode cur = head;
        while (cur.next != null){
            if (cur.next.val==val){
                ListNode del =cur.next;
                cur.next=del.next;
            }
            cur=cur.next;
        }
    }
    public void removeAllKey(int val) {
        //1. 判空
        if(this.head == null) {
            return;
        }
        //2. 定义prev 和 cur
        ListNode prev = head;
        ListNode cur = head.next;
        //3.开始判断并且删除
        while(cur != null) {
            if(cur.val == val) {
                prev.next = cur.next;
                //cur = cur.next;
            }else {
                prev = cur;//prev = prev.next;
                //cur = cur.next;
            }
            cur = cur.next;
        }
        //4.处理头节点
        if(head.val == val) {
            head = head.next;
        }
    }
    public void clear() {
        //head = null;
        ListNode cur = head;
        while (cur != null) {
            ListNode curN = cur.next;
            //cur.val = null;
            cur.next = null;
            cur = curN;
        }
        head = null;
    }


}
